1. Field of the Invention
The present invention relates to an optical storage capable of reducing power consumption. More particularly, the present invention designs a disk-receiving space into a structure capable of reducing skin friction, flow resistance and torque, which are generated on the surface of a disk and within a housing owing to the flow of fluid in vicinity of the disk in the high speed rotation of the disk, thereby to reduce power consumption, noise and vibration of an optical storage or a hard disk drive.
2. Description of the Related Art
Optical storages are an apparatus for storing (recording) or regenerating (retrieving) voice, image and text data based upon optical laser technology. The optical storages include CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD+RW, DVD-RW, MMVF, HD DVD drives. Disks used by the optical storages may have various diameters such as 2.5, 3.5, 4.72, 5.25 and 12 inches.
An optical storage of this type generally turns a disk at a high speed in order to rapidly and stably record, read and retrieve massive data.
The high-speed rotation of the disk causes various problems such as strong turbulence, flow resistance, friction and fluttering induced from the flow of fluid in a space around the disk. These problems may also create vibration and noise thereby increasing power consumption.
This is particularly disadvantageous in case of a notebook computer since a battery of the notebook computer will be more rapidly exhausted thereby to reduce run time.
FIG. 1 is a cross-sectional view illustrating a housing loaded with a disk in a conventional OMS, and FIG. 2 is a graph illustrating a skin friction coefficient curve with respect to the distance from the disk center in the OMS shown in FIG. 1.
As shown in FIG. 1, the conventional OMS housing is spaced at predetermined distances from the top and underside of the disk, but does not provide any structure or configuration for improving the flow of fluid in the rotation of the disk.
In the OMS housing, an upper height H1 from the top of the disk 10 to the ceiling of the housing 1 is generally different from a lower height H2 from the bottom of the housing 1 to the underside of the disk 10. This causes pressure difference between above and under the disk 10 in the high-speed rotation thereof, and the pressure difference also functions as a factor of fluttering during the rotation of the disk 10.
In the high-speed rotation of a disk, the pressure around the disk decreases in proportion to the square of the circumferential velocity from the center of the disk to the outer circumference so as to produce high pressure in a central portion of the disk and low pressure in an outer circumferential portion of the disk. This as a result generates vibration and noise to the disk as well as increases power consumption because of increase in flow resistance. This phenomenon becomes more significant according to the increase of the difference between the upper and lower heights.
High-speed rotation of the disk inside the optical storage creates strong turbulent motion or turbulence, which in turn collides against the side wall of the housing 1 generating vibration and noise. The flow of fluid around the disk sharply increases skin friction and torque at the circumference of the disk thereby elevating power consumption.
As shown in FIG. 2, the skin friction coefficient curve rises sharply around the circumference of the disk. The sharp rise of the skin friction coefficient curve will have a large value when integrated, and therefore can increase power consumption since power consumption is proportional to the integrated value of a skin friction coefficient curve as will be described later.
As a drawback, the conventional optical storage consumes more power because of the above-described fluttering, turbulent fluctuation and increase in skin friction and torque around the circumference of the disk
A solution to this problem was disclosed in Korean Patent Application No. 1998-13873, entitled “Apparatus for Reducing Noise in an Optical Disk Drive.” This document proposes grooves formed in the top of a tray, by which radial flow generated in the rotation of a disk is converted perpendicularly or toward the center of rotation of the disk.
By modifying the configuration of the tray, this solution aims to remove the velocity gradient in a boundary layer occurring on the surface of a disk as well as to prevent the collision of high speed air flow occurring on the leading end of the disk thereby reducing noise and vibration.
FIG. 3A is a plan view of a conventional tray having a helical groove formed on the top thereof (as disclosed in Korean Patent Application No. 1998-13873), and FIG. 3B is a cross sectional view of the tray shown in FIG. 3A with a disk loaded thereon.
As shown in FIGS. 3A and 3B, a groove 3 is formed in the top of a tray 2 under a disk 10 so that any velocity gradient induced from radial flow under the disk 10 can be removed. However, this structure has only a limited capability for decreasing skin friction or torque induced from fluid flowing in a radial direction of the disk, and therefore can reduce power consumption by an insignificant quantity.
That is, similar to the graph shown in FIG. 2, a skin friction coefficient curve sharply rises in vicinity of the outer circumference of the disk and therefore increases the integrated value thereof so that power consumption is also increased from the relation between power consumption and skin friction coefficient as will be described later.
Furthermore, since this apparatus modifies only the tray 2 under the disk 10, but does not provide any means for preventing flow resistance occurring on the top or side of the disk 10 owing to fluid fluctuation. Accordingly, this apparatus still has a problem in that it cannot obtain an effect of reducing skin friction, noise or vibration.
This apparatus also cannot fundamentally prevent fluttering induced from the pressure difference between above and under the disk in the high speed rotation of the disk and therefore the increase of flow resistance and skin friction.
This problem is equally observed not only the optical storage but also a Hard Disk Drive (HDD) which turns a disk at a high speed. Therefore, the following description of the specification and the claims can be applied not only to general optical storages but also to HDDs for reading data from a disk, which rotates at a high speed, or storing data into the disk.